The US is ready to ramp up pressure against North Korea through additional penalties, secondary sanctions and a tighter implementation of UN resolutions, Secretary of State Rex Tillerson said Wednesday, adding “a lot of work” is left to maximize its strategy.

“So it’s a pressure campaign that has a knob on it. I’d say we’re at about dial setting five or six right now, with a strong call of countries all over the world to fully implement the UN Security Council resolutions regarding sanctions, because no one has ever fully implemented those,” Tillerson said at a meeting with State Department employees.

“When we see you not implementing, we see companies or we see individuals that are violating these sanctions ... we’ll sanction them through third-country sanctions.”

US Secretary of State Rex Tillerson addresses State Department employees on May 3. (Reuters-Yonhap)

Since US President Donald Trump was sworn in Jan. 20, North Korea has been high on its foreign policy agenda. Following a monthslong policy review, his administration has recently settled on its approach, dubbed “maximum pressure and engagement.”

But the former real estate magnate has sent mixed signals on the communist state. Earlier this week he fueled criticism after saying he would be “honored” to meet with Kim and calling him a “smart cookie.” In the preceding weeks, military tension simmered as Washington redirected an aircraft carrier strike group toward the peninsula and top officials warned Pyongyang “not to test” the US’ resolve in the wake of its strikes in Syria and Afghanistan.

The speech set the stage for Tillerson to brief his own staff on the North Korea strategy and other top foreign policy priorities under Trump’s “America First” agenda, including relations with China, Russia and other world powers as well as the fight against the Islamic State extremist group.

The top diplomat said Washington’s pressure campaign is at about the “20 to 25 percent stage,” warning Pyongyang against further punitive steps should it carry out another major provocation.

“Thus far, our assessment is it is going like we had hoped for in terms of the response we’re getting from others, but we’ve got a lot of work left to do to keep that pressure on,” Tillerson said.

“We are preparing additional sanctions, if it turns out North Korea’s actions warrant additional sanctions. We’re hopeful that the regime in North Korea will think about this and come to a conclusion that there’s another way to the future.”

The Trump administration’s efforts to press and persuade China over the North Korea issues represent its resolve to “test” the prevalent assumption that Beijing has limited influence and willingness to assert it on Pyongyang, the secretary said.

But he reiterated that the campaign is not intended to bring about a regime change in the North or forced reunification. Washington remains open to talks, but only when the Kim Jong-un leadership shows a genuine commitment to denuclearize, he said.

“So that’s what we’ve been doing, is leaning hard into China to test their willingness to use their influence, their engagement with the regime in North Korea,” Tillerson said.

“We are ready and prepared to engage in talks when conditions are right. But as you’ve heard me say, we are not going to negotiate our way to the negotiating table.”

Seoul took note of the secretary’s reference to the secondary sanctions and intensified pressure, saying it once again emphasizes the Trump’s administration’s commitment to tackle the North Korean nuclear issues.

“As it has said at a UNSC ministerial conference last week, the US is forecast to take a full range of concrete steps to reinforce the international community’s sanctions and pressure against the North,” Foreign Ministry spokesperson Cho June-hyuck said at a news briefing Thursday.

“We have been also consulting with the US and other partners on ways to take strong, effective responses if North Korea commits an additional nuclear test, intercontinental ballistic missile launch or other strategic provocation.”

The US Congress has also been shoring up efforts, pushing for a bill to relist the North as a state sponsor of terrorism and other measures. The House of Representatives is expected to pass legislation for new North Korea sanctions as early as Thursday.